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Notes: Long-term fumigation with different mixtures of air pollutants, such as O3, NO2 and SO2, in combination with potassium deficiency in 4-year-old spruce trees shows clearly that the photosynthetic apparatus reacts very sensitively to environmental stress. Even when no change in photosynthetic oxygen evolution of the leaves was measurable, the content of D-1 protein in the reaction center of photosystem II already increased significantly at low stress conditions. With increasing concentrations of pollutants, the content of D-1 protein decreased considerably. This pattern was observed with all combinations of gases, although they differed in effectiveness. The most potent effect on the content of D-1 protein was found with a combined fumigation of SO2 plus NO2. Obviously, the ratio between synthesis and degradation of the D-1 protein is influenced by stress factors. However, the content of D-1 protein was not strongly correlated with photosynthetic oxygen evolution in whole needles nor with electron transport rate in isolated thylakoids. Under controlled potassium deficiency, effects similar to those observed upon ozone fumigation developed. The results suggest unspecific stress answers for the D-1 content and the photosynthetic reactions rather than specific responses.

Notes: Selected high alpine plant species were collected from different elevations in the Obergurgl/Ötztal subnival and nival regions in Austria to investigate the content of antioxidants in plants growing under the particular in vivo conditions experienced in this area (e.g. chilling stress, short vegetation period and high irradiation). The contents of antioxidants (ascorbic acid, tocopherol and glutathionc) and photosynthetic pigments were measured throughout the day. The contents of most compounds were found to follow a diurnal rhythm, with the maximum occurring at midday and the minimum during the night. It was not clear whether these fluctuations were temperature-dependent or light-dependent.Analyses of the antioxidant spectrum in the same plant species at different altitudes (and thus under different environmental conditions: as altitude increases, for example, day temperature decreases and light intensity increases) revealed that the total amount of antioxidants increases as altitude increases. This enhancement was mainly due to ascorbic acid contents. Each plant species displayed a specific reaction to the increase in stress that accompanies an increase in altitude, resulting in a broad adaptation spectrum for these plants. The present study suggests that the combined effect of lower temperature and higher light intensity induces higher antioxidant contents.

Notes: Two clones of 5-year-old Norway spruce [Picea abies (L.) Karst.] were exposed to two atmospheric concentrations of CO2 (350 and 750 μmol mol−1) and O3 (20 and 75nmolmol−1) in a phytotron at the GSF-Forschung-szentrum (Munich) over the course of a single season (April to October). The phytotron was programmed to recreate an artificial climate similar to that at a high elevation site in the Inner Bavarian Forest, and trees were grown in large containers of forest soil fertilized to achieve contrasting levels of potassium nutrition, designated well-fertilized or K-deficient. Measurements of the rate of net CO2 assimilation were made on individual needle year age classes over the course of the season, chlorophyll fluorescence kinetics were recorded after approximately 23 weeks, and seasonal changes in non-structural carbohydrate composition of the current year's foliage were monitored. Ozone was found to have contrasting effects on the rate of net CO2 assimilation in different needle age classes. After c. 5 months of fumigation, elevated O3 increased (by 33%) the rate of photosynthesis in the current year's needles. However, O3 depressed (by 30%) the photo-synthetic rate of the previous year's needles throughout the period of exposure. Chlorophyll fluorescence measurements indicated that changes in photosystem II electron transport played no significant role in the effects of O3 on photosynthesis. The reasons for the contrasting effects of O3 on needles of different ages are discussed in the light of other recent findings. Although O3 enhanced the rate at which CO2 was fixed in the current year's foliage, this was not reflected in increases in the non-structural carbohydrate content of the needles. The transfer of ambient CO2-grown trees to a CO2-enriched atmosphere resulted in marked stimulation in the photosynthetic rate of current and previous year's foliage. However, following expansion of the current year's growth, the photosynthetic rate of the previous year's foliage declined. The extent of photosynthetic adjustment in response to prolonged exposure to elevated CO2 depended upon the clone, providing evidence of intraspecific variation in the long-term response of photosynthesis to elevated CO2. The increase in photosynthesis induced by CO2 enrichment was associated with increased foliar concentrations of glucose, fructose and starch (but no change in sucrose) in the new growth. CO2 enrichment significantly enhanced the photosynthetic rate of K-deficient needles, but there was a strong CO2soil interaction in the current year's needles, indicating that the long-term response of trees to a high CO2 environment may depend on soil fertility. Although the rate of photosynthesis and non-structural carbohydrate content of the new needles were increased in O3-treated plants grown at higher levels of CO2, there was no evidence that elevated CO2 provided additional protection against O3 damage. Simultaneous exposure to elevated O3 modified the effects of elevated CO2 on needle photosynthesis and non-structural carbohydrate content, emphasizing the need to take into account not only soil nutrient status but also the impact of concurrent increases in photochemical oxidant pollution in any serious consideration of the effects of climate change on plant production.

Notes: Abstract Effects of high temperatures on the leaves of Ranunculus glacialis were studied in plants taken from sites located between 2400-2550 m in the Central Alps. Changes in CO2 exchange rates, in vivo chlorophyll fluorescence, and cellular ultrastructure were investigated during and after an experimental heat exposure. The earliest heat stress effect was inactivation of the net photosynthetic rate at 38-39 °C. Between 40-42 °C, disorders appeared in the photosynthetic apparatus and in the tonoplast. Heat shock granules were observed at 42 °C in chloroplasts, and at 44 °C also in mitochondria. In this temperature range, the dark respiration rate was reversibly enhanced, and an increased number of polyribosomes indicated repair after the primary injury. Above 44 °C, the degradation progress entered the phase of chronic impairment leading to irreversible damage at 45-46 °C. An unusually wide temperature range from the start of reversible photosynthetic inhibition to incipient necrosis indicated a pronounced heat sensitivity, particularly in cellular functions, of this arctic-alpine species.

Notes: Summary Etioplasts of dark grown plants contain a large paracrystalline prolamellar body (PLB) and, attached to this there are prothylakoid membranes (PTs). PLB-tubules inAvena are composed mainly of two saponins and include only a low percentage of other lipids, protochlorophyll(ide) and proteins. Following the development of etioplasts in darkness from the very beginning until plants loose turgescence one can observe marked changes in ultrastructure. In the early stage of development predominantly PTs are seen in small etioplasts. Wide-type PLBs are small. After eight days there is a well developed stage with the well-known big and highly crystalline PLBs, which are connected to many long PT-membranes. After 13 days the PLBs are not significantly changed, while number and length of PTs are strongly reduced. These morphological observations are quantified by measurements of PLB-area and PT-length per plastid section. Saponin content as a marker for PLB-tubules and protochlorophyll(ide)-content as a marker for PT-membranes were measured. Both methods of determination show in good agreement a peak of development for PTs around day 6–7, and for PLBs around 9–10. Beginning senescence affects PT-membranes and PChl(ide) strongly, while saponins resp. PLBs persist better. These results are presented in view of thylakoid formation during greening, starting from the different etioplast stages.

Notes: Summary This communication will give a general survey, leading to some new or altered ideas on the development and meaning of prolamellar bodies (PLBs) and prothylakoids (PTs) in etiolated tissue. The following main characteristics are discussed starting from an overview of our data concerning differences between PLBs and PTs, and in relation to results, published by others. (1) It is assumed that there is no common structural concept for the diversity in growth pattern of PLB-tubules. (2) Formation of PLBs with wide spacing or narrow spacing of tubules is determined by the ability of a plant to form special saponins in darkness. (3) PLBs develop as an outgrowth from perforated sheets, formed mainly by a process of self assembly of saponins. The perforations already may be originate by assembly of these compounds in the growing membrane. (4) A hypothesis is presented on regulation of PLB-development by light/dark regimes: Chlide formation influences via several steps the biosynthetic pathway at C15 to form either steroids (darkness) or prenyllipids (light). This is discussed in view of phytol metabolism Thus, PLBs are seen as a secondary product of membrane formation in darkness, while the PT-membranes possess the apparatus for a fast greening process.